Monoclonal gammopathy of undetermined significance (MGUS) is a condition in which an abnormal protein — known as monoclonal protein or M protein — is in your blood. The protein is produced in a type of white blood cell (plasma cells) in your bone marrow.
MGUS usually causes no problems. But sometimes it can progress over years to other disorders, including certain forms of blood cancer like multiple myeloma.
MGUS occurs when abnormal plasma cells produce M protein often in adults over the age of 40. The protein isn't harmful for most people. But if too much M protein accumulates, it crowds out healthy cells in your bone marrow and can damage other tissues in your body.
There are three main types of MGUs and based on the size and type of expression a doctor may advise frequency of screening
|Type of MGU||Description|
|Non-IgM MGUs||This is the most common type of MGUs seen in the body and has the potential to progress to multiple myeloma|
|IgM MGUs||About 15% - 20% of patients express the IgM MGU. It can potentially progress to a rarer form of cancer called as "Waldenstrom macroglobulinemia" and rarely to multiple myeloma|
|Light chain MGUS (LC-MGUS)||These MGUS can progress to a condition in which a certain type of M protein is found in the urine protein (Bence Jones proteinuria) and develop into light chain multiple myeloma|
PLASMA CELL NEOPLASMS or cancers in the plasma cell are classified as the following as per WHO guidelines
|Monoclonal gammopathy of undetermined significance (MGUS)||No Sub-types|
|Osteosclerotic Myeloma (POEMS Syndrome)||No Sub-types|
There are 2 common systems of staging the disease. Both are comprehensive
|Disease Stage||Hemoglobin Level||Serum Calcium||Bone X ray||M-Component Proteins|
|Stage I||10g/dl||Normal levels or 12mg/dl||Normal or solitary plasmacytoma||
|Stage II||Stage III > values > stage I||Stage III > values > stage I||Stage III > values > stage I||Stage III > values > stage I|
||Advanced Stage lesions||
|Stage II||Neither Stage I or Stage III|
|Stage III||Serum β2-microglobulin > 5.5 mg/L|
|Type of Plasmacytoma||Description|
|Solitary Plasmacytoma of Bone||
This occurs earlier than multiple myeloma (almost as long as a decade earlier) and is more common in males
SPEP is ideally negative but in almost 50% of the patients a low level of M protein may be present. Bone Marrow usually does not show increased plasma cells
The common sites of involvement are the nasal cavity, nasopharynx, larynx and sinuses. It can happen in any location in the body and is commonly of the IgA sub-type. Other evidence of systemic Multiple Myeloma is typically absent
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